HTTP Compliance: improve age calculation.

Account for response delay in age calculation as described in RFC 2616 section
13.2.3.

Co-Advisor test cases:
    test_case/rfc2616/ageCalc-none-7-none
    test_case/rfc2616/ageCalc-5400-4-5

=== modified file 'src/store.cc'
--- src/store.cc	2010-09-01 05:07:21 +0000
+++ src/store.cc	2010-09-28 03:48:39 +0000
@@ -1487,63 +1487,66 @@ StoreEntry::validToSend() const
 {
     if (EBIT_TEST(flags, RELEASE_REQUEST))
         return 0;
 
     if (EBIT_TEST(flags, ENTRY_NEGCACHED))
         if (expires <= squid_curtime)
             return 0;
 
     if (EBIT_TEST(flags, ENTRY_ABORTED))
         return 0;
 
     return 1;
 }
 
 void
 StoreEntry::timestampsSet()
 {
     const HttpReply *reply = getReply();
     time_t served_date = reply->date;
     int age = reply->header.getInt(HDR_AGE);
-    /*
-     * The timestamp calculations below tries to mimic the properties
-     * of the age calculation in RFC2616 section 13.2.3. The implementaion
-     * isn't complete, and the most notable exception from the RFC is that
-     * this does not account for response_delay, but it probably does
-     * not matter much as this is calculated immediately when the headers
-     * are received, not when the whole response has been received.
-     */
+
+    /* Compute the timestamp, mimicking RFC2616 section 13.2.3. */
+
     /* make sure that 0 <= served_date <= squid_curtime */
 
     if (served_date < 0 || served_date > squid_curtime)
         served_date = squid_curtime;
 
     /*
      * Compensate with Age header if origin server clock is ahead
      * of us and there is a cache in between us and the origin
      * server.  But DONT compensate if the age value is larger than
      * squid_curtime because it results in a negative served_date.
      */
     if (age > squid_curtime - served_date)
         if (squid_curtime > age)
             served_date = squid_curtime - age;
 
+    // compensate for Squid-to-server and server-to-Squid delays
+    if (mem_obj && mem_obj->request) {
+        const time_t request_sent =
+            mem_obj->request->hier.peer_http_request_sent.tv_sec;
+        if (0 < request_sent && request_sent < squid_curtime)
+            served_date -= (squid_curtime - request_sent);
+    }
+
     if (reply->expires > 0 && reply->date > -1)
         expires = served_date + (reply->expires - reply->date);
     else
         expires = reply->expires;
 
     lastmod = reply->last_modified;
 
     timestamp = served_date;
 }
 
 void
 StoreEntry::registerAbort(STABH * cb, void *data)
 {
     assert(mem_obj);
     assert(mem_obj->abort.callback == NULL);
     mem_obj->abort.callback = cb;
     mem_obj->abort.data = cbdataReference(data);
 }
 
 void